There has always been a need for an accurate, durable and relatively inexpensive sensor to sense the level of liquid fuel such as in a vehicle's fuel tank. A desirable level sensing device should have few moving parts and the active portions of the device should be protected from damage and contamination as well as be separated from the fluid itself.
U.S. Pat. No. 2,439,092 to Linstrom discloses an apparatus for indicating pressure having a bowed electrical contacting element and a diaphragm to flex into the element.
U.S. Pat. No. 3,242,731 to Colgan discloses a differential pressure indicating device having a bowed, bendable resistor element.
U.S. Pat. No. 2,651,939 to Weaver discloses a level sensing device with a submerged housing and a tubular element for venting the housing and for leading wires therefrom to the top of a tank.
U.S. Pat. No. 2,943,302 discloses a device for sensing pressure including a curved resistor board and a pivotal contact assembly.